Disable testVerifyToolbarButtonsLabelAndAction on device.

This test is failing reliabily on the iOS 10 device bots.

TBR: edchin
Bug: 772186
Change-Id: If08dcce9410a2d8884fc455f0b33b7ba2f6801c9
Reviewed-on: https://chromium-review.googlesource.com/703999
Commit-Queue: Mike Baxley <baxley@chromium.org>
Reviewed-by: Mike Baxley <baxley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#506912}

ios/showcase/toolbar/sc_toolbar_egtest.mm

@@ -41,9 +41,17 @@ using ::showcase_utils::Close;
   [super tearDown];
 }
 
+// TODO(crbug.com/772186): Fails on iOS 10 devices.
+#if TARGET_IPHONE_SIMULATOR
+#define MAYBE_testVerifyToolbarButtonsLabelAndAction \
+  testVerifyToolbarButtonsLabelAndAction
+#else
+#define MAYBE_testVerifyToolbarButtonsLabelAndAction \
+  DISABLED_testVerifyToolbarButtonsLabelAndAction
+#endif
 // Tests if the Toolbar buttons have the right accessibility labels and
 // commands.
-- (void)testVerifyToolbarButtonsLabelAndAction {
+- (void)MAYBE_testVerifyToolbarButtonsLabelAndAction {
   // Buttons displayed in both Regular and Compact SizeClasses.
   // Back Button.
   [[EarlGrey